This invention relates to innovative connectors and fasteners that make buildings stronger, and helps protect them from earthquakes, hurricanes, tornadoes, and strong winds.
Recent studies of earthquake damage on wood-frame buildings indicate that the outside wall sheathing is the most important structural member in preventing destruction to a home. Sheathing that is tightly secured to a house, stiffens the vertical components against damaging deformations.
The initial failure location on buildings during hurricanes is at the roof to wall connection, or at the wall to floor connection. This invention uses the outside wall sheathing to help tie the roof and floor to the walls, and stiffens the wall to distribute wind loads to the roof framing and end walls.
Failure and loss of the roof sheathing is common during hurricanes, mainly because of inadequate fastening of the roof sheathing to the underlying structural members. The roof system provides stability to a house by supporting the tops of exterior and interior load-bearing walls.
Sheet metal joints perform better than nailed joints in high winds and during seismic activity. Strong connectors, secured by sturdy fasteners, will insure that the major structural members of a house are securely tied together. Rigid outside sheathing, securely fastened to the walls, strengthens the link between the horizontal and vertical components of a structure.
Earthquake studies of a single-family building showed that failure was mainly due to the improper connection of wall studs to sole plates; the failures were attributed to nail withdrawal from the framing (Goers, 1976).
Tests of wall studs to sole plate connections showed that the studs were uplifted from the sole plate, and the nails which connected the bottom of the plywood sheathing to the sill were punched out of the sheathing (Kamiya et al., 1981).
The outside sheathing allows the naturally flexible wood wall studs to deform just enough to absorb the earthquake forces without cracking. When the outside sheathing is secured tightly to the studs, top plate, rafter, and sole plate, without becoming disconnected, it increases their load-bearing strength.
Steel connectors, between different components of a wood-frame buildings superstructure, provide continuity so that the building will move as a unit in response to seismic activity (Yanev, 1974). Outside sheathing helps transfer earthquake forces to the ground while greatly strengthening the resistance to lateral seismic motions (Yanev, 1974).
In 1974, wind-study testing of a full-scale house showed that the initial failure location was at the roof to wall connection, or at the wall to floor connection (Tuomi and McCutcheon, 1974). The stiffness of the wall influences the distribution of wind loads to the roof framing and end walls (Polensek, 1976).
In 1990, tests were done on (prior art) rafter/top plate connectors (hurricane clips) that are installed on a house during construction; it was found that hurricane clips are sometimes three to five times stronger than conventional toe-nailing under uplift loads (Canfield, 1990). Retrofit of prior art hurricane clips is difficult or impossible on existing houses.
Studies of damage from Hurricanes Andrew and Iniki show that most of the wind damage to a gable end of a home was from the difference in pressure inside and outside the home. Almost all pictures of damaged wood or masonry buildings show the gable end blown away from the building. (FEMA reports FIA-22, FIA-23)
Pictures never show the gable end blown into the building. This is due to the Bernoulli Effects, where the pressure differential between wind blowing around and over a building, and high pressure air inside, blows out a wall or roof.
An airplane rises due to the pressure differential of faster air moving over a wing, compared to the high pressure of slower moving air under a wing. So too does the side walls blow out of a house due to the Bernoulli effects of wind blowing perpendicular to the wall. Gable ends blow out of a house, because of higher pressure in the house compared to the extremely low pressure on the leeward edge of the wind direction.
Once the side wall or gable end of a house is blown out, the rigidity of the roof and entire house is compromised due to wind getting into the house. Driven rain, along with the wind can damage everything in the house, along with damaging the structural integrity of the roof and walls of the house.
Loss of the roof sheathing was consistently observed after Hurricane Iniki and Hurricane Andrew. The primary cause of sheathing damage was inadequate nailing into the underlying structural members of the roof. There was evidence of missing, corroded, misapplied, and too few nails or staples attaching the roof sheathing to the rafters, purlins, or trusses.
If an earth tremor is strong, the nails holding the outside wall sheathing may be inadequate in size or quantity. Many nails are driven into the edge of the sheathing where the wood can split and lose connection with the underlying studs.
If the outside sheathing detaches from the wall studs, the walls cannot transfer lateral forces or transverse loads and the building can rack and collapse. When the outside sheathing is sufficiently attached to the structural framing, the sheathing and structural framing function together.
A sturdy wall system absorbs, resists, and transfers forces imposed by wind and earth movements. Improperly secured sheathing may not function effectively in resisting transverse loads and lateral forces.
Previously, framers did not understand the structural importance of outside wall sheathing. Improper nail size, length, or type, along with an improper fastening schedule, could jeopardize the anchoring ability of the outside sheathing. Plywood can still be applied with power-driven staples.
Many times, the exterior sheathing is applied to the wall when it is constructed on the ground, then raised in place. This helps keep the wall from racking when raised, but is heavier to lift and may be weaker than sheathing applied to a wall in place.
Part of my co-pending application, Ser. No. 08/191,852, filed on Feb. 2, 1994, ties the rafter to the outside sheathing and underlying top plate. This is one of the weakest failure points on a house during a hurricane.
This continuation-in-part application has unique connectors to tie together major structural members of a house using the important outside sheathing. These major structural members include the gable end rafter and joist, the sole plate and walls, and the corner post, rafter, and top plate. These unique connectors are held to the outside sheathing, and underlying or exposed structural members using unique fasteners, or nails, screws, and bolts.
The stability of the walls is dependent on the roof for top lateral support. The roof sheathing can be composed of boards or plywood. It ties the rafters and roof trusses together, and prevents the roof from racking. The roof sheathing may have been applied carelessly in the past, as it was felt that the weight of the roof cladding would keep the roof on tight.
Previously, framers did not understand the structural importance of roof sheathing. Improper nail Haze, length, or type, along with an improper fastening schedule, could jeopardize the anchoring ability of the roof sheathing. Plywood may be applied with power-driven staples. In humid or salt-air climate, the nails or staples can corrode and lose holding power.
A number of connectors have been developed to tie together the roof rafter and the top plate, or wall stud and sole plate. Previous connectors were made to be used during construction of the structure and covered by the outside sheathing.
These connectors cannot be retrofitted to existing structures without extensive dismantling or damage to the inside wall board or outside sheathing. Without dismantling the walls, a homeowner can""t tell if hurricane clips are correctly fastened to their house. Older homes usually don""t have hurricane clips or any type of sheet metal connectors installed on their house to prevent racking, or movement between structural members.
Prior tie connectors are also limited to the number of roofing and structural members that can be tied together. Since prior connectors are made for installation on the frame-work of a building, they cannot tie the outside sheathing to a building. All previous connectors were designed to be covered over by the outside sheathing. Since they do not tie the outside sheathing to the underlying structural members of the house, they cannot prevent the house from racking in an earthquake or wind storm.
The roof lock in U.S. Pat. No. 1,452,599 to Hames, March 1922, and the dock bracket in U.S. Pat. No. D.290,223 to Westerheim, June 1987 did not tie the rafter to the top plate and outside sheathing. The hurricane tie in U.S. Pat. No. 4,714,372, December 1987, and snugging connector in U.S. Pat. No. 4,896,985, January 1990, both to Commins, can tie the rafter to the top plate in the skeleton structural framework of new construction. They can not be used as a retrofit on existing houses; they did not tie the sheathing to the top plate and rafter; they did not go around the frieze board; they did not tie into a stud or top plate directly underneath a rafter; and they did not tie together two 2xc3x974""s of the top plate.
The bearing connector in U.S. Pat. No. 5,109,646, May 1992, to Colonias et al. is used to carry roof loads, but can tie together a rafter, top plate, and two 2xc3x974""s of the top plate together in the skeleton structural framework of new construction. This connector can not be used as a retrofit on existing houses; it did not tie the sheathing to the top plate and rafter; it did not go around the frieze board; and it did not tie into a stud or top plate directly underneath a rafter.
The building construction ties in U.S. Pat. No. 2,300,113, to Faber, October 1942, can tie the rafter to the joist and wall stud in the skeleton structural framework of new construction. They can not be used as retrofit on existing houses; they did not tie the sheathing to the top plate and rafter; they did not tie the rafter and top plate together or go around the frieze board; and they did not tie together two 2xc3x974""s of the top plate.
The free gusset metal ledger hanger in U.S. Pat. No. 4,353,664, to Gilb, October 1982, is used to provide ledger support around the inside perimeter of buildings or at internal concrete or masonry walls. This connector can not be used as a retrofit on the outside of existing houses; it did not tie the sheathing to the top plate and rafter; it did not tie together a rafter and top plate; it did not go around the frieze board; it did not tie into a stud or top plate directly underneath a rafter; and it did not tie together two 2xc3x974ls of the top plate.
The wall tie in United Kingdom patent 2,096,664, to Durrant, October 1982, is used to strengthen mortar joints in brick walls. This connector can not be used as a retrofit on the outside of existing wood houses; it did not tie the sheathing to the top plate and rafter; it did not tie together a rafter and top plate; it did not go around the frieze board; it did not tie into a stud or top plate directly underneath a rafter; and it did not tie together two 2xc3x974ls of the top plate.
The connecting plate for wood members in Germany patent 238,822, to Sauer, March 1986, is used to connect planks, boards, or strips, using bending slots and nail holes. This connector, by its large bending slots, is a weak connector. Bending this connector weakens the metal, especially since most carpenters would hammer the connection to make it fit on planks and boards. This connector is useful for attaching together boards that intersect at odd angles, not equal to 90 or 45 degrees. This connector may be used as a retrofit on existing houses, but was intended for attaching beams and planks in the skeleton structural framework of new construction. It did not tie the sheathing to the top plate and rafter or go around the frieze board; it did not tie into a stud or top plate directly under a rafter; and it did not tie together two 2xc3x974""s of the top plate.
The metal connectors in Switzerland patent 214,358, April 1941 are used to connect wood and metal members together. The connectors can tie I-beams, angle iron, and wood boards to metal frames in skeleton structural framework of new construction. They can not be used as retrofit on existing houses; they did not tie the sheathing to the top plate and rafter; they did not tie the rafter and top plate together; they did not go around the frieze board or tie into a stud or top plate directly under a rafter; and they did not tie together two 2xc3x974""s of the top plate.
The apparatus and method for securing a building during high winds in U.S. Pat. No. 5,319,986 to Winger, June 1994, is used to secure several of the roof rafters to the ground by cables and anchors. This system is employed only when high winds are expected, as the cables must be extended and attached to the ground anchor manually. In a post-and-beam constructed house where the inside rafters are exposed, the cables and attaching hardware are exposed to view. Cables can kink, stretch, rust in place, and break. This system did not tie down the roof sheathing or roof shingles. This system will not work if the homeowner is not home to secure the anchoring cables. It cannot work in areas where tornadoes can occur without warning, especially if the home owner is sleeping or is seeking shelter in the basement or interior room. The system requires extensive and expensive carpentry work and expensive hardware.
The house anchor in U.S. Pat. No. 1,864,403, to Bradley, June 1932, uses cables and ground anchors to secure the roof to the ground. It did not tie together the rafter and ridge plate or tie them straight down to the ground; since the rafter and ridge plate are not secured together and tied to the ground on the gable end of the house, the house is vulnerable to winds on the side of the house that can push or pull and separate the gable end of the rafter plate to ridge plate connection. Cables can stretch and break. Parts of the house anchor include eye-bolts and cable guides which can pull out from wood when subjected to perpendicular pulling forces as from strong winds.
The exterior anchoring apparatus for surface sheets in U.S. Pat. No. 1,864,403, to Bradley, March 1967, uses metal rods and clamps to secure exterior sheathing to a roof. This system cannot be retrofit to an existing roof. It did not tie the sheathing securely to the rafter and ridge board.
Objects and Advantages
Accordingly, several objects and advantages of my invention are that it helps hold the gable and hip ends of a building from being blown in or out by hurricanes, tornadoes, and wind storms.
This invention helps prevent the outside sheathing of the gable and hip ends on existing buildings from detaching during an earthquake. It also allows some deflection in the joint without separating. The invention tightly holds the outside sheathing to the roof rafter, top plate, joist, and wall stud using unique, but simple and economical connectors and fasteners.
Objects of this invention are that it easily, quickly, and economically protects buildings from the destructive effects of earthquakes. It is a further object of this invention that it easily, quickly, and economically protects houses from the destructive winds of hurricanes. It is a still further object that the connectors and fasteners are strong, attractive, permanent, functional, uncomplicated, simple to manufacture, easy to install, and economical. Many of the embodiments can be made from a single sheet metal blank, without any welding.
Another objective is for the rafters or roof trusses to be secured together and locked to the wall and roof sheathing. The invention can be used as an accurate spacer for trusses and for attic ventilation. This invention can be used during construction and can be retrofit onto existing homes.
The installation procedure is simple so that a handy homeowner can install the connectors and fastener hardware. Except for expensive, custom-built homes, most homeowners had no input or knowledge on how strong their houses are built. Now homeowners can retrofit their homes by themselves or with a hired contractor. Installation of this invention will make a house more resistant to strong winds and seismic activity.
Since the invention is mostly on the outside of a house, it is unadorned, but can be covered with the homeowners choice of wood trim, veneer, gingerbread, other architectural facades, or can just be painted to match or contrast with the house.
Previous disasters showed that many nailed connections on destroyed or damaged homes were undersize, mis-installed, or completely missing. By being installed on the outside of a house, an inspector, homeowner, or insurance agent can see if there are any missing connectors and fasteners. Since the bushings are made of the correct size and material, no undersize or wrong material fasteners can be installed.
Masonry houses don""t fare well during an earthquake because the house can""t flex, it usually snaps instead. This invention allows the sheathing connection on a house to deflect or flex by using a bushing and bearing surface for low friction.
The outside sheathing is one of the most important structural members when a house is under stress of hurricane-force winds or seismic activity. This invention helps prevent the wood of the outside sheathing from splitting. It also holds the outside sheathing securely to the underlying structural members.
None of the prior art connectors hold on the outside sheathing, because they went on a house before the outside sheathing was installed. None of the previous connectors use a bushing and bearing surface to allow motion, and still hold the sheathing and underlying structural members together.
There are several embodiments of this invention in order to fit on as many different types of houses as possible. Several embodiments of this invention protect most types of wood-frame construction. Numerous houses, including brick and concrete-block, have the gable end constructed of wood. Several embodiments of this invention protect most types of masonry houses constructed with wood gables.
A further object is that this invention can be used on various size houses. A still further object is that the embodiments of this invention are retro-fit onto new and old homes made of wood or masonry. There may be insurance discounts for homeowners who have this invention installed.
These and other objectives of the invention are achieved by a system of simple and economical connectors and fasteners that allow a homeowner or contractor to quickly and easily protect the weakest parts of a building against earth tremors and high winds.
Advantages of each will be discussed in the description. Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.